In general, a silver halide black-and-white photographic material which has been exposed to light is then subjected to processing procedures, including black-and-white development, fixing, rinsing, etc. A silver halide color photographic material (hereinafter referred to as "color photographic light-sensitive material") which has been exposed to light is then subjected to processing procedures, including color development, desilvering, rinsing, stabilization, etc. A silver halide color reversal photographic material which has been exposed to light is then subjected to processing procedures, including black-and-white development and reversal, followed by color development, desilvering, rinsing, stabilization, etc.
In the color development procedure, silver halide grains which have been exposed to light are reduced with a color developing agent to silver, while the resulting oxidation product of the color developing agent undergoes reaction with a color coupler to form a dye image.
In the subsequent desilvering procedure, developed silver which has been produced in the development procedure is oxidized (bleached) with a bleaching agent (oxidizer) having an oxidative effect to form a silver salt. The photographic material is then processed with a fixing agent to form a soluble silver which is eventually removed from the light-sensitive layer together with unused silver halide (fixing). Bleaching and fixing may be effected separately as a bleaching step and a fixing step, or may be effected simultaneously as a blixing step. For details of these processing procedures and compositions, reference can be made to James, "The Theory of Photographic Process", 4th edition, 1977, and Research Disclosure Nos. 17643 (pp. 28-29), 18716 (left column - right column, p. 651), and 307105 (pp. 880-881).
In addition to the foregoing basic processing procedures, various auxiliary procedures may be conducted for maintaining the photographic and physical quality of dye image or processing stability or like purposes. Examples of these auxiliary procedures include a rinsing procedure, a stabilizing procedure, a hardening procedure, and a stop procedure.
In order to adjust the gradation or like properties of a silver halide black-and-white photographic material which has been developed, a reducer containing an oxidizer is used.
The oxidizer incorporated into the processing solution for use in the foregoing bleaching or reducing procedure is typically ferric ethylenediaminetetraacetate complex salt or ferric 1,3-diaminopropanetetraacetate complex salt, which compounds are not biodegradable. In recent years, from the standpoint of environmental protection, it has been desired to render the waste liquid from these photographic processing procedures harmless to human beings. In particular, easily biodegradable processing compositions have been desired. Substitutes for the foregoing unbiodegradable bleaching agents have been studied.
Biodegradable bleaching agents that have been proposed include ferric complex salt of N-(2-carboxymethoxyphenyl) iminodiacetic acid as disclosed in West German Patent Application (OLS) 3,912,551 and ferric complex salt of .beta.-alaninediacetic acid or glycinedipropionic acid as disclosed in European Patent Application 430000A. However, processing solutions having a bleaching capacity containing these bleaching agents leave much to be desired in desilvering properties. These processing solutions have been found to be disadvantageous in that when used in continuous processing, their desilvering properties are gradually lowered as the processing proceeds and bleaching fog is increased, or the processed photographic materials tend to become stained with time.
In these color processing systems, small-sized automatic developing machines called miniature laboratories have recently become wide spread to provide rapid processing service to customers. Accordingly, the stability of photographic properties in continuous processing is indispensable, notwithstanding the need for rapid bleaching.
Furthermore, again from the standpoint of environmental protection, it has been desired to lower the concentration of metal chelate compounds used as bleaching agents. However, the foregoing bleaching agents cannot provide sufficient desilvering properties at low concentrations.